The term stranger is the traditional way of referring to someone physically present in the Palace of Westminster who is neither a member of parliament nor a parliamentary official. In 2004, a motion was approved implementing the recommendation of the Modernisation Committee that the term stranger no longer be used and be replaced with either member of the public or the public.
Nowadays, visitors can watch debates, and can sit in the Strangers' Gallery. Historically, visitors were not allowed in at all. Parliament still has the right to debate in private, and any visitor causing a disturbance can be ejected, or even taken into custody by the Serjeant at Arms. The House of Commons rarely goes into private session (the last occasion being on 4 December 2001 when it was debating the Anti-Terrorism, Crime and Security Bill), and although much routine business is handled by Select Committees, Second Reading and Third Reading and usually attracts little attention, most main debates are public. Although BBC Parliament now broadcasts from the main debating chambers of both the House of Commons and House of Lords, as well as from important committees which may meet outside the chambers, it must turn off sound transmission during divisions.
Attempts to exclude visitors are usually employed simply to disrupt or delay the House's proceedings, a kind of filibustering. An MP wishing to interrupt used to shout "I spy strangers". The Speaker must then immediately put the motion "That strangers do now withdraw", as a point of order. If the motion was carried, the public galleries were cleared — this could (but rarely did) include the press gallery and Hansard; broadcast television and radio stops, and business continues in private. This was Standing Order No. 163 of the House. It has been amended as part of modernisation of Commons business, but the principle remains much the same.